Why is UIScrollView leaving space on top and does not scroll to the bottom

Just select your view controller and set shown option to false (uncheck)

1... Why is UIScrollView leaving space on top

With Storyboard- Goto view controller > Attribute Inspector > Uncheck Adjust Scroll View Insets property

With Code- For extra space set viewController property automaticallyAdjustsScrollViewInsets to NO, by default it is YES.

self.automaticallyAdjustsScrollViewInsets = false; 
scroller.contentInset = UIEdgeInsetsZero;
scroller.scrollIndicatorInsets = UIEdgeInsetsZero;
scroller.contentOffset = CGPointMake(0.0, 0.0);

2... does not scroll to the bottom

To make it scroll try with large number in contentSize like CGSizeMake(320, 1687). If it works that means you are not setting the contentSize large enough to have all its content.